Megaflow questions

[gardinerg]

Hi guys and gals, I am hoping you can help me. I recently moved in to a house with a Megaflow (with red expansion tank) and I notice that the pressure valve underneath drops over time (a couple of days). I can top this up by opening the inline valve (also underneath it) for 30 seconds or so, but I guess I shouldn't have to?

(I recently had to replace the 2 broken mixer showers (the plumber I called out didn't really know much about the unvented systems but suggested I turned the mains off, which worked when he did it). )

I have tried regenerating the bubble and there are no signs or noises of water leaking that I can hear (maybe it's an air leak on a PRV ??).

After replacing the showers I was disappointed by the shower pressure, it was then I noticed the low pressure in the expansion tank and subsequent drop after re-filling.

Whilst I am not a plumber by trade or certification I would appreciate some explanation of how the expansion tank should opperate and does this behaviour change with the hot water off or not? Would I be right in saying never to leave the fill valve open under the expansion tank?

I assume the shower pressure will improve and be consistent if the pressure in the system is correct and stable, is that correct?

I think the system is faulty and needs some tlc so am probably going to need a experienced (in unvented systems) plumber who works around Fleet, Hampshire... Don't worry, I have NO intention on touching the system beyond the basic ownership requirements, I just like to know how things in my house work.

Thanks in advance for your help,

P.s. the big lack valve on the inlet to the Megaflow will not close, at least not with my limited strength!

Cheers

Grant

 

[gardinerg]

Sorry, a quick update... I have noticed the pressure increases to about 1.5 bar when the heating is on (like now!).

 

[dancinplumba]

hi the red expansion vessel is for you heating system, if you are constantly having to top it up you have a leak somewhere and need to get a professsional in to sort it for you

 

[stevetheplumber]

gauge and red vessel are part of your heating system and have no bearing on hot water preasure the big black valve is a preasure reducing valve which is preset usually three bar)and not adjustable most likley cause of reduced preasure is the main stopcock hasnt been turned on fully or you have a blockage in the filter which is part of the preasure reducing valve

 

[AWheating]

if you are unsure about the unvented cylinder installation then i would suggest you get it serviced. It is supposed to be service/checked every year anyway so for peace of mind and all that. Any questions about the system can be answered by the engineer at the time.

make sure you check the engineer is qualified to work on unvented hot water systems.

 

[gardinerg]

Ok thanks for the helpfull replies! Follow up question...

The tundish beneath the expansion tank is wet/damp - seemingly, where it joins the bottom pipe.


Is this just another symptom of the pressure being lost (via expansion tank/prv) or a separate issue (faulty tundish??)?

Ta

 

[dancinplumba]

would appear so but tundish is also connected to tprv and prvv on unvented cyl, you eed a professional to look at it

 

[dontknowitall]

Another symptom. As suggested by AWHeating I'd ask a chappie in (make sure he can do unvented cylinders as not all plumbers do them). If you explain problem during phone call he might be able to sort it out in the one visit (thereby saving you a few pounds).

 

[Hardy1]

can you see a tundish? or is it just me blind?

 

[mikegas]

can you see a tundish? or is it just me blind?

Just behind 2 port in pic 3

 

[Gray0689]

Lol someone tuck the time to paint all the pipe work silver lol very nice just a pity it's all meant to be lagged

 

[Nat]

It's likely your expansion vessel has lost its charge and needs recharging or replacing. When the water in your heating system is heated it expands in volume by about 4%. This is usually accomodated by the vessel but if is not doing its job the water will discharge from the pressure release valve, PRV, and when the water cools it loses volume again and that's when your pressure goes down.

The pressure in your shower is unrelated to this but as stated before be a good idea to check the filter on the combination valve on the main in the cylinder cupboard.